The Jet Fuel Thermal Oxidation Tester (JFTOT) is used by the Air Force to determine the thermal stability of JP-4 and JPTS type fuels. A device called the Tube Deposit Rater (TDR) has been proposed as a means of evaluating the deposits formed on JFTOT tubes. (Author) Concern has existed about the need to account for the pretest condition of the test tubes. The effect of pretest ratings is discussed in the report and a method is proposed for improving results by accounting for the pretest condition of the tubes. (Author).

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Various aspects of the thermal stability problem associated with the use of broadened-specification and nonpetroleum-derived turbine fuels are addressed. The state of the art is reviewed and the status of the research being conducted at various laboratories is presented. Discussions among representatives from universities, refineries, engine and airframe manufacturers, airlines, the Government, and others are presented along with conclusions and both broad and specific recommendations for future stability research and development. It is concluded that significant additional effort is required to cope with the fuel stability problems which will be associated with the potentially poorer quality fuels of the future such as broadened specification petroleum fuels or fuels produced from synthetic sources.

The Visual Rating method and the ALCOR Mark 8A Tube Deposit Rater, used to rate deposits that form on the Jet Fuel Thermal Oxidation Tester (JFTOT) heater tubes, were compared to each other and to measurements of the deposit thickness. An Auger Electron Spectrometer, used in conjunction with an ion gun (AES/Ion Gun), was used to measure the deposit thickness and composition. Both the Visual Rating method and the Mark 8A Tube Deposit Rater were found to correlate with deposit thickness measurements to a limited degree. The AES/Ion Gun method proved to be a useful laboratory tool for measuring the relative thickness of deposits and the elemental composition of deposits (except for hydrogen and helium). Deposits that have a spectrum of colors (i.e., peacock or rainbow type deposits) were found to be considerably thicker than Code 3 deposits. Thin film light interference was found to be the cause of the peacock associated with these deposits.